Field of the Invention
The present invention relates to wireless communications, and more particularly, to a communication method of an advance user equipment (UE) using a second frequency when a legacy UE uses a first frequency for a downlink and the second frequency for an uplink in frequency division duplex (FDD).
Related Art
Long Term Evolution (LTE) based on 3rd Generation Partnership Project (3GPP) Technical Specification (TS) Release 8 is the leading next-generation mobile communication standard.
As disclosed in 3GPP TS 36.211 V8.7.0 (2009-05) “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8)”, in LTE, a physical channel can be divided into a Physical Downlink Shared Channel (PDSCH) and a Physical Downlink Control Channel (PDCCH), that is, downlink channels, and a Physical Uplink Shared Channel (PUSCH) and a Physical Uplink Control Channel (PUSCH), that is, uplink channels.
A PUCCH is an uplink control channel used to send uplink control information, such as a Hybrid Automatic Repeat reQuest (HARQ), an acknowledgement/not-acknowledgement (ACK/NACK) signal, a Channel Quality Indicator (CQI), and a Scheduling Request (SR). Currently, 3GPP LTE-Advanced (LTE-A) as an evolved version of 3GPP LTE is progressing.
Meanwhile, a conventional wireless communication system uses either of time division duplex (TDD) and frequency division duplex (FDD). TDD is a technique where the same frequency band is used for an uplink and a downlink at different times. FDD is a technique where different frequency bands are used for an uplink and a downlink. FDD uses two different frequency bands to allow uplink and downlink transmissions simultaneously, whereas TDD does not allow simultaneous uplink and downlink transmissions.
When FDD is used, in which a downlink and an uplink use the same frequency band, resources are allocated to the downlink and the uplink at a fixed ratio of 1:1. However, when data traffic is concentrated in either of the downlink and the uplink, the resources may not be efficiently used.
Thus, it is necessary to modify a conventional TA determination method for a wireless communication system in which cells using different duplexing modes may be aggregated.